Osteonecrosis and Resorption of the Patella After Total Knee Replacement

A 54-year-old woman with a history of right total knee replacement had right knee pain and swelling for 6 months. Radiographs of the knee showed significant fragmentation and resorption of the patella consistent with osteonecrosis. Evidence of increased anteroposterior laxity was noted on physical examination. Revision surgery to a posterior stabilized prosthesis with excision of the patellar fragments resulted in a marked improvement in her symptoms and functional capabilities 2 years after surgery. The authors review the blood supply to the patella and how it may be disturbed by knee surgery and speculate that this patient's symptoms may have been worsened by the anteroposterior instability of her prosthesis.